1. Field of the Invention
The present invention relates to a recording tape cartridge which rotatably accommodates a single reel onto which a recording tape, such as a magnetic tape or the like, which is used as a recording/playback medium of a computer or the like, is wound.
2. Description of the Related Art
Conventionally, magnetic tape cartridges have been known in which a magnetic tape, which is used as a data recording/playback medium of a computer or the like, is wound on a single reel and the reel is accommodated within a plastic case. A leader member, such as a leader block or a leader pin, for example, is provided at a distal end (free end) of the magnetic tape. A drawing-out means, which is provided at a drive device, pulls out the leader member from the magnetic tape cartridge, so that the magnetic tape fixed to the leader member is wound onto a take-up reel of the drive device.
A reel gear is carved in an annular shape at a center of a bottom surface of the reel which emerges from an opening formed in a bottom surface of the magnetic tape cartridge. Due to a driving gear, which is provided at a rotating shaft of the drive device, meshing with the reel gear, the reel is driven to rotate. Further, due to the reel of the magnetic tape cartridge and the take-up reel of the drive device being rotated synchronously, writing and reading of information on the magnetic tape can be carried out.
Such magnetic tape cartridges have leader members provided at the distal ends of the magnetic tapes, as described above. In the case of a leader block 70, as shown in FIG. 5, an opening 76 of the magnetic tape cartridge can be closed off by the leader block. The leader block 70 has an outer wall surface 72 which is outwardly exposed from the opening 76 and provided with a rear end portion 72B. The leader block also has a front end portion 72A and a concave portion 74 which is next to the front end portion and with which a drawing-out member 60 of a tape drive comes into engagement. By the rear end portion 72B being hooked at a front end portion 82B of a right wall of a case 80 and by the front end portion 72A being hooked at a right end portion 82A of a front wall of the case 80, the leader block 70 can be retained so as to close off the opening 76.
More specifically, the front wall right end portion 82A of the case 80 has a slit 78 formed at an interior thereof by which the right end portion 82A is elastically deformable in a front-back direction of the case 80. Due to such an elastically deformable means formed on the case side, the leader block 70 can be detachably hooked and retained with respect to the case 80. A force of the case 80 for holding the leader block 70 is sufficient to prevent the leader block 70 from easily falling from the case 80 even with the application of shocks due to dropping and the like.
Further, when the opening 76 is closed of by the leader block 70, the magnetic tape T is pulled and held by a predetermined tension in a winding direction of a reel (not shown in the drawings) so as to prevent slack and the like which may occur within the case 80. Therefore, when the leader block 70 is drawn out from the case 80 by the drawing-out member 60 of the tape drive side, some load is applied to the magnetic tape T, even though the reel is driven to rotate. Consequently, it is necessary that a force of the drawing-out member for drawing out the leader block 70 surpasses the load applied to the magnetic tape T and the holding force of the case 80 without the risk of elongation or breakage of the magnetic tape T.
Namely, it is necessary that the leader block 70 is suitably retained by the case 80 when the magnetic tape cartridge is not in use and that the leader block 70 is easily detachable from the case 80 when the magnetic cartridge is in use. Therefore, force-balancing between the drawing-out force exerted by the drawing-out member 60 and the holding force exerted by the case 80 must be appropriately maintained through delicate adjustment. Until now, such an adjustment has been effected by adjusting an elastically deformable means that is formed on the case side or by adjusting an elastic force of the front wall right end portion 82A that is formed with the slit 78.
Generally, cases of magnetic tape cartridges have a variety of mechanisms formed on outer surface portions thereof and are often subjected to modification and the like. If such a means for holding a leader block to a case is provided at the case side in this typical way, a degree of freedom of design of the case is adversely affected such that there are many more constraints on the case structure. Further, since the above-described force-balancing must be realized at the case side, the cost of manufacturing the cases is inevitably increased.